SX440 AUTOMATIC VOLTAGEREGULATOR(AVR) SPECIFICATION,INSTALLATION AND ADJUSTMENTSGeneral description SX440 is a half-wave phase-controlled thyristor typeAutomatic Voltage Regulator(AVR) and forms part of theexcitation system for a brush-less generator. In addition to regulating the generator voltage, the AVRcircuitry includes under-speed and sensing lossprotection features. Excitation power is derived directlyfrom the generator terminals. Positive voltage build up from residual levels is ensuredby the use of efficient semiconductors in the powercircuitry of the AVR. The AVR is linked with the main stator windings and theexciter field windings to provide closed loop control of theoutput voltage with load regulation of +/-1.0%. In addition to being powered from the main stator,theAVR also derives a sample voltage from the outputwindings for voltage control purposes. In response to thissample voltage,the AVR controls the power fed to theexciter field,and hence the main field, to maintain themachine output voltage within the specified limits,compensating for load,speed, temperature and powerfactor of the generator. A frequency measuring circuit continually monitors thegenerator output and provides output under-speedprotection of the excitation system,by reducing the outputvoltage proportionally with speed below a pre-settablethreshold. A manual adjustment is provided for factorysetting of the under frequency roll off point,(UFRO).Thiscan easily be changed to 50 or 60 Hz in the field by push-on link selection. Provision is made for the connection of a remote voltagetrimmer, allowing the user fine control of the generator'soutput. An analogue input is provided allowing connection to aNewage Power Factor controller or other external deviceswith compatible output. The AVR has the facility for droop CT connection,to allowparallel running with other similarly equipped generators. Technical specification INPUT Voltage 190-264V ac Frequency 50-60 Hz nominal Phase 1 Wire 2 OUTPUT Voltagemax 90V dc at 207V ac input Currentcontinuous 4A dc Intermittent 6A for 10 secs Resistance 15 ohms minimum REGULATION +/-1%(see note 1) THERMAL DRIFT 0.04% per deg.C change in AVR ambient(note 2)